Various X-ray techniques, such as grazing-incidence X-ray fluorescence (GIXRF), are used for materials characterization in many fields, including in semiconductor devices. Examples of prior art techniques are provided below.
U.S. Pat. No. 6,381,303, to Vu, et al., whose disclosure is incorporated herein by reference, describes an X-ray micro-analyzer for thin films, which irradiates a spot having a dimension less than 500 μm on a surface of the sample. A first X-ray detector captures fluorescent X-rays emitted from the sample, responsive to the irradiation, at a high angle relative to the surface of the sample. A second X-ray detector captures X-rays from the spot at a grazing angle relative to the surface of the sample. Processing circuitry receives respective signals from the first and second X-ray detectors responsive to the X-rays captured thereby, and analyzes the signals in combination to determine a property of a surface layer of the sample within the area of the spot.
U.S. Pat. No. 6,829,327, to Chen, et al., whose disclosure is incorporated herein by reference, describes an improved total-reflection X-ray fluorescence (TXRF) apparatus using a doubly-curved optic for use in detecting foreign matter on surfaces, such as, on semiconductor wafers.
U.S. Pat. No. 7,039,158, to Janik, et al., whose disclosure is incorporated herein by reference, describes a thin film analysis system which includes multi-technique analysis capability. Grazing incidence X-ray reflectometry (GXR) can be combined with X-ray fluorescence (XRF) using an electron beam to excite X-rays that are measured with a wavelength-dispersive X-ray spectrometry (WDX) detectors to obtain accurate thickness measurements with GXR and high-resolution composition measurements with XRF using WDX detectors.
U.S. Pat. No. 6,108,398, to Mazor, et al., whose disclosure is incorporated herein by reference, describes an X-ray fluorescent analyzer and method for analyzing a sample, including an X-ray beam generator, which generates an X-ray beam incident at a spot on the sample, and creates a plurality of fluorescent X-ray photons. There are a plurality of semiconducting detectors arrayed around the spot so as to capture the fluorescent X-ray photons and in response produce a plurality of electrical pulses suitable for analysis of the sample.
U.S. Pat. No. 7,062,013, to Berman, et al., whose disclosure is incorporated herein by reference, describes a method for inspection of a sample that includes a first layer having a known reflectance property and a second layer formed over the first layer. The method includes directing radiation toward a surface of the sample and sensing the radiation reflected from the surface so as to generate a reflectance signal as a function of elevation angle relative to the surface.
U.S. Pat. No. 7,258,485, to Nakano, et al., whose disclosure is incorporated herein by reference, describes an X-ray thin film inspection apparatus including a sample table on which an inspection target such as a product wafer or the like is mounted, a positioning mechanism for moving the sample table, a goniometer having first and second swing arms, at least one X-ray irradiation unit that are mounted on the first swing arm and containing an X-ray tube and an X-ray optical element in a shield tube, an X-ray detector mounted on a second swing arm, and an optical camera for subjecting the inspection target disposed on the sample table to pattern recognition.
U.S. Pat. No. 6,173,036, to Hossain, et al., whose disclosure is incorporated herein by reference, describes Depth profile metrology using grazing incidence X-ray fluorescence. A series of X-ray fluorescence measurements are performed at varying small angles and analyzed for depth profiling of elements within a substrate.
Further theory and details of GIXRF are provided by Klockenkämper, in “Total Reflection X-ray Fluorescence Analysis,” John Wiley & Sons, 1997, chapters 2-4, which is incorporated herein by reference.
Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.